rfc - Changing the way gitk and git-gui are managed

Somebody off-list suggested removing gitk and git-gui directories from my repository and I've been playing with the idea and kind of like the end result.

The plan (I am not decided to buy into it yet, hence I am sending this rfc) is to:

    - remove gitk-git and git-gui directories;
    - add modules/gitk and modules/git-gui submodules;
    - teach the top-level Makefile about the new location of these two
      packages.

Switching from 1.7.2 to this tree will of course give you a tree without gitk and git-gui (nothing a simple "git submodule init/update" cannot fix), and switching back from there to 1.7.2 codebase needs manual removal of these two directories that will become leftover directories if you want to keep the superproject directory pristine clean, but other than that, I do not see major downsides.

I am wondering what people think. Especially distro people who download and package git may be heavily affected. I haven't adjusted the RPM spec file or "make dist" target, so I cannot assess the damage to these people myself yet.